The present invention relates generally to a direct current brushless motor.
DC motors have long been used in the power field and in the commercial marketplace. Traditionally, these motors make use of field windings and an armature which is energized by brushes through a commutator. In general, these motors work very well and are very efficient. Some motors make use of permanent magnets for the field, but this is limited. Typically, maintenance on these motors is not too much of a concern until they are operated in a harsh environment, which causes wear on the brushes. Most motors are carefully designed for specific applications based on the horsepower and speed required.
The following United States patents are of interest.
4,973,869--Cho PA1 4,857,783--Prunkard PA1 4,220,879--Hoshimi et al PA1 3,579,277--Imahashi
The patents identified above relate to various designs for brushless, direct current (DC) motors. In particular, the Cho patent describes a disc type brushless, cordless, DC motor. The motor comprises a rotor, stator, armature coil, and a position detector sensor. The position detector sensor is installed below an effective coil part of the armature coil. A single screw, having a rounded head, is installed at the position one-fifth of a magnetic pole width apart from the position detector sensor. This type of placement provides for larger starting torque with lower starting voltage. The Prunkard patent is directed to a brushless DC motor which comprises a rotor, a magnetic leaf switch, and a ferrous core coil winding. The rotor incorporates a flat, annular two pole permanent magnet and a rotational output shaft passing through the magnet. The magnetic leaf switch floats in the magnetic field of the permanent magnet. The ferrous core coil winding serves as a stator which is energized by direct current. Current flow to the stator is controlled in an alternating on-off manner by the magnetic leaf switch. When the stator is energized, the core assumes a polarity that repels one of the poles of the permanent magnet carried by the rotor. This repulsion causes rotation of the permanent magnet about the longitudinal axis of the rotational output shaft. The Hoshimi et al patent relates to a brushless DC motor comprising a rotor, stator and detecting elements. The rotor includes a rotor magnet, with a number of poles, mounted on a rotor yoke which in turn is mounted on a rotor shaft. The stator includes a stator yoke and a number of stator coils disposed on the stator yoke to face the rotor magnet in a non-overlapping predetermined angular relation to each other. Wiring means are disposed on the stator yoke and are connected to the stator coils. The detecting elements are mounted on the wiring means to sense the rotational position of the rotor magnet and provide a signal by which current fed to the stator coils can be controlled. The Imahashi et al patent relates to a brushless DC motor. Pairs of axially spaced permanent magnets are radially arranged about and fixed to a rotor shaft, and driving coils are disposed in the space between the pairs of permanent magnets. A shield ring having cutaway Portions is disposed in the path of detecting coils so that when the cutaway portions are aligned with positional detecting coils, the driving coils associated with the particular detecting coils, are activated to produce a driving force.